How to use an AVAudionPlayer soundtrack within a method? iOS

I have an if method that picks out a random background. I have called this method within the didMoveToView so every time the view is loaded, the method will be executed and a random background will be set. If the background first becomes either 0 or 1, the app crashes and i think it's because if the background is NOT the sea then it's trying to stop a soundtrack that hasn't been started yet... Any ideas on how to solve this ?

//PICKS A RANDOM BACKGROUND EACH TIME THE SCENE IS LOADS
-(SKSpriteNode*) pickRandomBackground {

   //this pick a random number between 0 and 2 then stores it
   NSInteger randomBackground = [Utility randomNumberAt:0 max:3];


    SKSpriteNode *background;





    //PYRIMID BACKGROUND
    if (randomBackground == 0) {


         background = [SKSpriteNode spriteNodeWithImageNamed:@"background2"];
        background.position = CGPointMake(CGRectGetMidX(self.frame), CGRectGetMidY(self.frame)+20);
        background.size = CGSizeMake(self.frame.size.width, self.frame.size.height);



    }

    //FOREST BACKGROUND
    if (randomBackground == 1) {

        background = [SKSpriteNode spriteNodeWithImageNamed:@"forestBackground"];
        background.position = CGPointMake(CGRectGetMidX(self.frame), CGRectGetMidY(self.frame));
        background.size = CGSizeMake(self.frame.size.width, self.frame.size.height);
    }

    //SEA BACKGROUND
    if (randomBackground == 2) {



        //SKY IMAGE
        background = [SKSpriteNode spriteNodeWithImageNamed:@"introbackground.png"];
        background.position = CGPointMake(CGRectGetMidX(self.frame), CGRectGetMidY(self.frame));
        background.size = CGSizeMake(self.frame.size.width, self.frame.size.height);
        background.zPosition = -1;

        //FOREGROUND SEA
        SKSpriteNode *foregroundSea = [SKSpriteNode spriteNodeWithImageNamed:@"foregroundsea"];
        foregroundSea.zPosition = 1;
        foregroundSea.size = CGSizeMake(self.frame.size.width+200, self.frame.size.width/3.0);
        foregroundSea.position = CGPointMake(CGRectGetMidX(self.frame),70);
        foregroundSea.anchorPoint = CGPointMake(0.5, 0.0);
        [self addChild:foregroundSea];
        [foregroundSea runAction:[SKAction waitForDuration:0.7] completion:^{
            [foregroundSea runAction:[self waveAnimation]];
        }];

        //BACKGROUND SEA
        SKSpriteNode *backgroundSea = [SKSpriteNode spriteNodeWithImageNamed:@"backgroundSea"];
        backgroundSea.zPosition = 0;
        backgroundSea.size = CGSizeMake(self.frame.size.width+200, self.frame.size.width/4.0);
        backgroundSea.position = CGPointMake(CGRectGetMidX(self.frame),100);
        backgroundSea.anchorPoint = CGPointMake(0.5, 0.0);
        [self addChild:backgroundSea];
        [backgroundSea runAction:[self waveAnimation]];


           //WAVE SFX
           [self.seaSFX play];
    }

if (randomBackground != 2) {
        [self.seaSFX stop];
    }


    background.zPosition = -1;
    [self addChild:background];
    return background;
}